Purifying iron with carbonic-acid gas



UNITED STATES P TENT OFFIQE.

JoHNF. BENNETT, or PITTSBURG, PENNSYLVANIA.

PURl FYlNG IRON WITH CARBONlC-ACID GAS.

SPECIFICATION forming part of Letters Patent l\ l'o. 85,786. dated October 2, 1883,

Application filed November 20, 1850; (No specimens.)

f0 an whom it may concern:

Be it known that I. JOHN FRANCIS BENNETT, a citizen of the United States, residing at Pittsburg, in the county of Allegheny and State of Pennsylvania, have invented certain new and useful Improvements in Purifying Iron with Oarbonic-Acid Gas, and I do hereby declare that the following is a full, clear, and exact description of the invention, which will en-' able others skilled in the art to which it -appertains to make and use the same.

, Heretofore pig and cast iron hayc been purified from excess of carbon in the manufacture of steel by blowing carbonic-acid gas through the metal when in a molten state, or by applying said gas intermixed with atmospheric air or steam to granulated pig or cast iron at atemperature sufficient to insure fluidity; also, crude, iron has been relieved of silicon, sulphur, phosphorus, and other impurities which form chemical combinations with the oxygen of the carbonic acid and deposit the carbon, by the use of carbonic aeid gas, either alone or mixed with atmospheric air,when introduced into the molten 1netal,im1nediately following the pneumatic process, which consists in the removal of the excess of carbon by subjecting the metal ,while in a. molten state, to an atmospheric blast, thereby producing combustion of the carbon and the requisite heat without sep arate fuel. n

The object of my invention is the purifica' tion of liquid iron from sulphur and phosphorus, after the silicon and excess of carbon have been removed, in an open-hearth furnace; and to this end my invention consists, first, in passin g carbonic-acid gas over and through it while in the open-hearth furnace and, second, tol keep such purified iron liquid, without disturbing the relative proportions of its constituent parts, until the impurities held in suspension therein have had time to rise to the surface as slag, which is readily isolated.

The difliculty to be contended with in utilizing the Bessemer converter for purifying iron by carbonic-acid gas is that when the pig-iron acted upon contains a large proportion of sulphur and phosphorus the passage through it of carbonic-acid gas sufficient to eliminate these impurities causes the metalto lose the gas, causing ebullition in the metal, and thus accelerating the operation. An undesirable feature in using the Bessemerconverter to de carburize pig-iron is the necessity of employ ing only that pig iron which contains silicon, in order to retain fluidity. Besides the fact that this consumption of silicon as a fuel is costly, it is found that the steel is deteriorated by being charged with a portion thereof, which mingles with the iron as silicate of iron. In my process the decarburized iron is poured into an open-hearth furnace,where all the heat requisitefor its further treatment is readily imparted without the necessary use of silicon. Any reverberatory furnace capable of sustaining the necessary temperature will suffice for this purpose. I would here name as a modification of this part of my invention that pig-iron, scrap wroughtiron, scrapsteel, and iron ore may be broughtinto the liquid state-in an openhearth furnace, as now practiced in the SicmensMartin process, and atmospheric air injected through the tuyeres, arranged as above described, until the bath of liquid iron is decarburized, after which carbonic-acid gas may be blown in. After this I proportionthe gases which constitute the hot flame that passes over the liquid bath in the opeirhearth furnace so that while they generate sufficient heat to keep the metal fluid they will not oxidize it. Iso

regulate this flame as to secure, in addition to the nitrogen incidentally present, a mixture of forty to forty-flve per cent. of carbonic oxthe quiescent state of the liquid metal, the scoria formed during the violent chemical reactions readily overcome the affinity by which they were held mechanicallyin the metal and rise to the surface. This should constitute the last course in the treatment.

Although I have separated my invention into two branches independent each of the other, it is obvious that they are consecutive steps in my process and dependent on each other to attain the single result. 7

Having thus fully described my invention, what I claim, and desire to secure by Letters Patent of the United States, is

In the purification of liquid iron and steel, the process of passing carbonioacid gas over and through the molten metal in an open-hearth furnace after the metal has been deearburized, whereby the sulphur and phosphorus are eliminated, and finally keeping the metal in a fluid state, without altering the proportions of the constituent elements, by passing over the liquid bath in said furnace equal quantities, ata common temperature, of carbonic-oxide gas and carbonic-acid gas, which so neutralize each other that the slag readily rises to the surface, all substantially as herein set forth.

JOHN FRANCIS BENNETT.

\Vitnesses:

A. O. JOHNSTON, FRANK PATTERSON. 

